It has been shown that high fat diet (HFD) induced obesity triggers local immune cell infiltration leading to pro-inflammatory cytokine production and subsequently to a state of chronic low-grade inflammation in adipose and spleen tissues. However, the underlying mechanisms driving this chronic inflammation remains poorly defined. The product of hexokinase (HK) enzymes, glucose-6-phosphate, can be metabolized through glycolysis to produce ATP and pyruvate or alternative pathways, such as the pentose-phosphate-pathway (PPP) to generate anabolic intermediates. HK1 contains an N-terminal domain that permits mitochondrial binding, but its physiologic significance is unclear. We found that adipose and spleen tissues from HFD mice had increased cytosolic HK1, which correlated with an increase in inflammatory cytokine mRNA levels. To elucidate whether HK1 subcellular localization to the mitochondria affects the inflammatory response we generated mice lacking the HK1 mitochondrial binding domain, termed ΔE1HK1. These mice appear normal and show no change in body weight, Mendelian ratios, glucose tolerance or hexokinase activity across different tissues as compared to littermate controls. However, lipopolysaccharide challenge in these mice produced a hyper-inflammatory phenotype in vitro and in vivo. We performed steady-state and flux metabolomics in ΔE1HK1 mouse tissues and found increased glucose derived metabolites above the level of GAPDH, including PPP metabolites. Additionally, we found that GAPDH activity was attenuated in the ΔE1HK1 mice and may explain the elevated PPP flux upstream of GAPDH. Since PPP is vital for proper inflammatory cell activation, we treated cells from these mice with PPP inhibitors and found a reversal of the hyper-inflammatory phenotype observed in ΔE1HK1 mice. Our data suggests that mitochondrial dissociation of HK1 alters glucose utilization, which subsequently increases the pro-inflammatory response.
F. Keyhani Nejad: None. A. DeJesus: None. J.A. Geier: None. H. Ardehali: None.